It's not wrong, Duo's just hasn't learned all possible translations yet :)
Dutch doesn't force you to use the present progressive tense to mark an ongoing activity.
You CAN say "Ik ben aan het drinken" to stress that right now, you are in the middle of doing it; but the present tense "Ik drink", "we drinken" etc. can be used and is used to express the same without the stress.
Besides that, the present tense also works like in English for general statements, e.g., what you habitually do: "Nee, ik drink nooit bier" (I never drink beer). So in Dutch you need more context to be sure which translation to choose, which is why Duo accepts both in this exercise:
We are drinking juice and eating cheese.
We drink juice and eat cheese.